5 Nov
2007
5 Nov
'07
10:44 p.m.
Throwing in a trace statement in fibaux tells me that fibaux i a b c is not being memoized. If I do map fib [7..9], fibaux counts down to 0 afresh for each of 7, 8, and 9. Ideally, in map fib [0..n], fib (i-2) and fib (i-1) should be memoized and fib i would be evaluated in constant time. This is what happens if the loop is unrolled explicitly. marnes wrote:
fib :: Integer -> Integer fib n = fibaux n 0 1 1 where fibaux :: Integer -> Integer -> Integer -> Integer -> Integer fibaux i a b c | i==0 = a | i/=0 = fibaux (i-1) b c (b+c)
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